PROJECT SUMMARY/ABSTRACT Delay discounting describes the devaluation of consequences (gains and losses) because they are delayed. When the value of a delayed consequence is discounted below the value of a smaller-sooner outcome, the latter is selected ? an impulsive choice. Longitudinal studies reveal that this type of discounting precedes and predicts adolescent drug taking and is correlated with a pattern of poor health decision-making. These findings raise the prospect of reducing impulsivity as a means of improving public health. Our laboratory has developed a delay-exposure (DE) training procedure that produces large and lasting reductions in rats' impulsivity. The proposed experiments will investigate three behavioral/cognitive mechanisms hypothesized to underlie the efficacy of DE training. Experiment 1 will evaluate if DE trained rats are more tolerant of delays (relative to control rats) by measuring their rate of escape from delay-signaling stimuli. Experiment 2 will determine if DE- trained rats demonstrate improved interval timing (precision and/or accuracy), and Experiment 3 will evaluate the hypothesis that DE training enhances detection of delayed-reinforcement contingencies. Identifying the mechanism(s) by which DE training reduces impulsivity is important because it will allow researchers to improve the efficiency and efficacy of impulsivity-reducing interventions. These interventions must be efficient and effective if they are to be incorporated into primary prevention programs designed to reduce the impulsivity that puts individual at risk of addictions and the poor health decision-making that leads to chronic disease (e.g., obesity).